Thermostat structure



Patented May 30, 1944 um'rso STATES PATENT OFFICE Q 'rnsamos'r a 'r 'znucruas v I Henry C. Bostwlck, Cranford, N. 1., asoignor to Westinghouse Electric & Manufacturing mpany, a corporation of Pennsyl Application December 22, 1942, Serial No. 469,821

4 Claims. (Cl. Mil-122) My invention relates to thermostat structures, and has for an object to provide an improved structure of this kind.

A further object of the invention is to provide an improved thermostat having a snap-acting, laminated metal, heat-responsive device which operates over a relatively wide range of temperatures.

These and other objects are eflected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a side view of an electric iron having my improved thermostat applied thereto;

Figs. 2 and 3 are, respectively, top and side elevations of the thermostat shown in Fig. 1; and

Fig. 4 is a diagrammatic view of the switching means forming a part of the thermostat shown in Figs. 2 and 3.

Reference will now be had to thedr'awing wherein I have shown my improved thermostatic structure, generally indicated at [0, applied to an electric iron, the base plate H of which is heated by an electric heating element 12 of any well-understood construction. The base plate I I is provided with a cover I3 which houses the thermostat l0 and which supports a handle 14. The iron is also provided with a second handle l5 for adjusting the thermostat l0 and, therefore, the temperatures at which the base plate ll operates, further reference to this adjustment being made hereinafter. V

Referring to Figs. 2 and 3, the thermostat I0 includes a supporting base It, notched asshown at IT, for the reception of mounting screws l8 which are threaded in the base plate ll of the This mounting proiron, as shown in Fig. 1. vides for the transfer of heat between the base plate II and the supporting base l6 of the thermostat. The supporting base I6 is provided with an upstanding boss is which is threaded inwardly, as shown at 21, to an adjusting stem,

the upper end of which is connected to the handle IS. The lower end of the adjusting stem 22 is rotatably mounted in an opening 22 formed in the center of a disc 24 which defines the heatrisponsive element of the thermostatic structure The disc 24 which is of laminated metal construction is dished, as shown in Fig. 3, and, when heated. changes its curvature with a snap action, as is well understood. The temperatures at which the disc snaps from one position to the other are adjusted by mechanically stressing the disc.; Rotation of the stem 22 clockwise as viewed in Fig. 3 lowers the central .-portion of the disc 24 and reduces the mechanical stress therein and. therefore, increases the temperature of the disc at which it snaps to its other position. Conversely, counterclockwise rotation oi the stem 22 raises the center of the disc 24 and increases the stress therein .so that it operates at reduced temperatures. As this operation is well understood, no further description oi the same is deemed necessary. The angular movement of the. stem 22 is limited by stops 2! and 28 carried by the boss 19 and engageable with a pin 21 extending radially from the stem 22. Conventional ad- Justable stops 28 are provided for engaging the disc 24 and limiting the reverse curvature of the disc.

The disc 24 carries a plurality of circumferentially-spaced contacts 29 which, in the closed position of the thermostat, engage a plurality of stationary contacts carried by the base l8 and insulated therefrom. The stationary contacts are best shown in Fig. 4 and are numbered 2| to 35, inclusive. As shown in Fig. 4, the heating element I2 is energiiied from a source of power" indicated by line conductors L1 and In the former of which is connected to one terminal of the heating element l2 and the latter of which leads to an upstanding terminal 38 connected to the stationary contact 33. .The opposite terminal of the heating element I2 is connected to an,

upstanding terminal 31 forming a part of the contact segment 22.

In order to reduce the temperature differential to the stationary contacts 2| and 25 and is energized in series with the main heating element l2 in the closed position of the thermostat III, as will be apparent from Fig. 4. In the open position of the thermostat, both elements l2 and 3 8 are deenergized.

- Theheater 38 is provided for supplementing the heat imparted to the disc 24 by the heated base ll during energized periods of the heating element l2. This operation is necessary as heatresponsive elements of the disc type having a tures of 350 .ture differentials of about 40 F. Disc type heati low operating temperaturh differential and wide iron, particularly of the steaming type, should be adjustable to maintain mean base tempera- F. to 550 F., and at base tempera- .hundred degrees while the base is heated 40 F. The use of a heater of the type shown at 22 has facilitated the manufacture of snap-acting thermostats but difliculty is still experienced in constructing thermostats which provide the relatively high temperatures demanded by steaming irons when ironing cotton goods.

In accordance with my invention, I propose toincrease the range of operating temperatures of the base H by rendering the heater 3! inactive in the high temperature setting. Accordingly, the heating of the disc 24 at this time is eflected only by heat received from the base Ill/so that the latter is heated to the cut-off temperature .of' the disc. The base temperature is, therefore,

of the order of 60 F. higher than it would be if the heater 3! were effective. With this operation, the range of temperatures of the base il i j and -the opposite terminal of the heater as.

When engaging the button 43, the switch member 4| shunts the heater 38 for deenergizing the same. In all positions of the adjusting stem 22 except the high-heat position, the resilient switch member is biased upwardly out of engagement with the button 43. In the high-heat position of the adjusting stem 22, the arm 21 engages a proplaced thereupon as are specifically .jection 44 carried by the switch member 4i and forces the latter into engagement with the. but- 'ton 43. This position of the apparatus is shown in the drawing. Upon movement of the stem 22 and its arm 21 counterclockwise to any of the lower temperature settings; the bias of the switch member 4i moves the same out of engagement with the button 43 and renders the heater 3! active. c From the foregoing p'arentthat I have effected an increase in the temperature range .of a thermostat of the type described by means readily attachable to such thermostats and without necessitating any major changes in the design thereof.

While I have shown my invention in but one description: it will be 89- element, said heater being energized and deenergized with said electrically energized means, and

a second switch operated by the adjusting means for rendering said heater inactive when the ad-, justing means is moved tothe position in which the heat-responsive element responds to maximum temperatures to operate the first-memtures of the heat-responsive element, an electric heater disposed in heat transfer relation with the heat-responsive element and controlled by said switch, means manually movable to a plurality of positions for adjusting said heat-responsive ele-,

ment whereby the temperatures to which the element responds to actuate the switch are varied, and means effective only in the position of the v manually movable means, wherein the heatresponsive element responds to'maximum temperatures to operate the switch, for rendering said electric heater inactive independently of said switch.

3. In a thermostat for controlling the temperature of..a body. having electrically energized means for heating the body, the combination of V a switch controlling energization of said electri- .cally energized means, a heat-responsive device for closing and opening said switch in response to predetermined low and high temperatures,

- respectively, means for adjusting said device for transfer relation with the device and connected form, it will be obvious to those skilled in the art the app nded claims.

What I claim is: 1. In a thermostat structure temperature of a body having electrically energized means for heating the body, the combina-- tion of a switch-for-controlling. energization of the electrically energized means, a heat-responset forth in for controlling the sive element disposed in heat transfer relation in series with said electrically energized means, a second switch shunted across the heater, and means for closing the second switch when the adjusting means is actuated to said high heat position.

4. In a thermostat, .a base, a plurality of insulated arcuate contacts carried by the base, -a .plurality of movable contacts for bridging adjacent ends of a portionof the arcuate contacts, an

of said. arcuate contacts, an electric heater connected across a second pair of the arcuate con- ,tacts, a heat-responsivelaminated metal disc supporting sai'd movable contacts and arranged adjacent saidelectric heater, means including a rotatable stem for adjustingsaid disc whereby the temperatures to which it responds to engage and disengage the movable and arcuate contacts 5 are varied, a switch shunted across said second contacts.

pair of arcuate contacts and said heater and 1 means carried by said stem for closing said switch HENRY c. Bos'rwrcx'.

engage the, movable and arcuate 

